Revolvers don't need it.
Well finished,high quality semi auto's don't need it.
Very tightly built,super high quality semi autos and other,less finished,semi autos need it.
In those cases,you should clean the gun,lube it right and shoot at least 200 to 300 rounds through it if you are going to depend on it to save your life.
You should shoot FMJ rounds when you do that break in period.
After the break in period,break it down,reclean it and lube it and retest it.
Obviously,you should test the JHP's you intend to use for self defense after the break in period.
That break in poeriod is recommened by a variety of manufacturers just to ease up the gun and mate the parts correctly.
It's not a flaw in the manufacturing.